1. Field of the Invention
The present invention relates to a sheet convey apparatus for conveying a sheet to a recording portion or a reading portion in a printer, a typewriter, a copying machine, a facsimile machine and the like, and more particularly, it relates to a sheet convey apparatus wherein a sheet can be fed in a direction perpendicular to a generatrix of a convey roller without skew-feed of the sheet and with high accuracy.
2. Related Background Art
As shown in FIG. 27, in a conventional recording apparatus 250, when a sheet P is set, the sheet P is rested on an inclined sheet supply tray 251, and then a knob 252 is rotated to wind the sheet P around a platen 253 once, and then the knob 252 is rotated reversely to disengage the sheet P from a nip between the platen 253 and a pinch roller 255. As a result, a leading or tip end of the sheet P is abutted against the nip between the platen 253 and the pinch roller 255 by the weight of the sheet, thereby positioning the sheet along the nip. Then, when the platen 253 is rotated normally, the sheet P is reliably conveyed in a direction perpendicular to the generatrix of the platen 253. The above method usually is used in conventional techniques.
However, in the conventional case shown in FIG. 27, after the sheet P is positioned along the nip between the platen 253 and the pinch roller 255, when the sheet is re-entered into the nip by rotating the knob 252 normally, since the urging force for abutting the tip end of the sheet P against the nip depends upon the weight of the sheet P itself, if a sheet supply direction becomes a direction near a horizontal direction, the urging force for abutting the sheet P against the nip is extremely weakened or eliminated, with the result that the sheet P cannot be re-entered into the nip.
Next, in the Japanese Patent Publication No. 62-38261, as shown in FIG. 28, a sheet P supplied from a pick-up roller 261 of a sheet supply device to a drive roller 262 is fed reversely until a tip end of the sheet passes through a nip of the drive roller 262, thereby forming a loop in the sheet P between the pickup roller 261 and the drive roller 262, so that the tip end of the sheet P is abutted against the nip of the drive roller 262. Thereafter, the sheet P is fed out by rotating the drive roller normally.
In the conventional case shown in FIG. 28, the urging force for abutting the tip end of the sheet against the nip of the drive roller 262 is not influenced by the sheet supply direction since such urging force depends upon the repelling force of the sheet P for restoring the looped sheet to its original flat form. However, since a loop must be formed in the rigid sheet P, a thick sheet cannot be used, and since a space and a convey path length sufficient to permit formation of the loop must be provided, it is difficult to make the apparatus small-sized.